The present invention relates to fixation pins for attaching a frame or immobilizing device to a bone structure of a patient with a skeletal injury, and, more particularly to a clamp for the rapid and accurate positioning of such fixation pins.
In cases of skeletal injuries, such as broken bones and cervical spinal injuries, it is often necessary to fix or stabilize the position of the bones while the injury heals. For example, such fixation may require the attachment of an external frame to long bones or the attachment of a halo orthosis to the skull of a patient. To attach such a frame or immobilizing device to a bone structure, fixation pins are commonly used. A common fixation pin comprises a threaded cylindrical body, a conical tip at the distal end of the cylindrical body for penetrating into a bone, and a head portion at the opposite end of the cylindrical body that is coupled to a means for rotating the fixation pin. Furthermore, in some constructions, a fixation pin has threads for engaging the bone itself, such as a fixation pin used for external fracture fixation. In any event, in a simple configuration, a first set of fixation pins is inserted percutaneously into a bone on a distal side of the fracture, and a second set of fixation pins is inserted percutaneously into a bone on a proximal side of the fracture.
Once the various fixation pins have been appropriately positioned and inserted in this manner, the fixation pins connected to a frame or similar immobilizing device through the use of pin clamps. Specifically, each fixation pin commonly includes a substantially smooth surface. A pin clamp is secured to the frame or similar immobilizing device and engages this substantially smooth surface of the fixation pin to grip and secure the fixation pin. In this regard, prior art pin clamps generally comprise a pair of opposing and facing clamping portions that collectively define one or more channels for receiving and retaining a fixation pin. These opposing and facing clamping portions are adjustably secured relative to one another by screws or similar fasteners. By tightening the screws or similar fasteners, the clamping portions are moved toward one another such that a fixation pin can be gripped and secured in one of the channels defined by the clamping portions. In this manner, the frame or immobilizing device to which the fixation pins are secured prevents or controls the movement of the bone near the fracture.
For further reference, various examples of prior art fixation pins and their uses are referenced and discussed in U.S. Pat. No. 6,159,210 issued to Voor, one of the present applicants. For such discussion and examples of prior art fixation pins and their uses, U.S. Pat. No. 6,159,210 is incorporated herein by reference.
Moreover, the above-referenced '210 patent describes an improved fixation pin. Specifically, the '210 patent describes and claims a fixation pin comprising a body with threads provided along a portion of its length, a cylindrical post coaxially secured to the leading end of the body, a rotary cutting tip formed in the face of the post, and a radial shoulder formed along the boundary of the body and the post. During insertion of this fixation pin, the pin is rotated, and the rotary cutting tip is advanced into the bone. The rotary cutting tip thus cuts a clean cylindrical hole into the bone without requiring a large axial force, while the radial shoulder limits the depth of penetration of the post into the bone. After insertion, the cylindrical post fits snugly in the hole, and no axial force is necessary to hold the fixation pin in place. The described fixation pin can thus be inserted and retained in the bone with a minimal axial force and with little damage to the surrounding bone and tissue. Furthermore, the construction of the fixation pin minimizes the possibly of loosening due to repetitive transverse loading.
Nevertheless, in prior art systems and methods, it remains common for fixation pins, regardless of their particular construction, to be inserted percutaneously into a bone before the complete assembly of the frame or similar immobilizing device. In other words, only after the pins have been appropriately positioned are the pin clamps used to engage the fixation pins and secure the fixation pins to the frame or similar immobilizing device. This sometime creates difficulties in ensuring proper pin positioning and also hinders the ability to tighten or otherwise adjust a fixation pin after placement and assembly of the frame or similar immobilizing device.
It is therefore an object of the present invention to provide a clamp that allows for rapid and accurate placement of a threaded fixation pin.
It is a further object of the present invention to provide a clamp that allows for fine adjustment of a threaded fixation pin after placement.
It is yet a further object of the present invention to provide a clamp that allows for temporary placement of a threaded fixation pin, thus allowing for assembly of a frame or immobilizing device without commitment to final pin positions.
These and other objects and advantages of the present invention will become readily apparent and addressed through a reading of the discussion below and appended drawings.